Self aligning non contact shadow ring process kit

ABSTRACT

The invention provides a removable first edge ring configured for pin and recess/slot coupling with a second edge ring disposed on the substrate support. In one embodiment, a first edge ring includes a plurality of pins, and a second edge ring includes one or more alignment recesses and one or more alignment slots for mating engagement with the pins. Each of the alignment recesses and alignment slots are at least as wide as the corresponding pins, and each of the alignment slots extends in the radial direction a length that is sufficient to compensate for the difference in thermal expansion between the first edge ring and the second edge ring.

BACKGROUND OF THE INVENTION

1. Field the Invention

The present invention relates to an improved susceptor which inhibitsthe deposition of process gasses on the edge and backside of asubstrate, and which may be easily removed and cleaned.

2. Background of the Related Art

Chemical vapor deposition (CVD) is one of a number of processes used todeposit thin films of material on semiconductor substrates. To processsubstrates using CVD, a vacuum chamber is provided with a susceptorconfigured to receive a substrate. In a typical CVD chamber, thesubstrate is placed into and removed from the chamber by a robot bladeand is supported by a substrate support during processing. A precursorgas is charged into the vacuum chamber through a gas manifold platesituated above the substrate, where the substrate is heated to processtemperatures, generally in the range of about 250° to 650° C. Theprecursor gas reacts on the heated substrate surface to deposit a thinlayer thereon and to form volatile byproduct gases, which are pumpedaway through the chamber exhaust system.

A primary goal of substrate processing is to obtain the largest usefulsurface area, and as a result the greatest number of chips, possiblefrom each substrate. This is highlighted by the recent demands fromsemiconductor chip manufacturers to minimize edge exclusion on thesubstrates processed, so that as little of the substrate surface aspossible, including the edge of the wafer, is wasted. Some importantfactors to consider include processing variables that affect theuniformity and thickness of the layer deposited on the substrate, andcontaminants that may attach to the substrate and render all or aportion of the substrate defective or useless. Both of these factorsshould be controlled to maximize the useful surface area for eachsubstrate processed.

One source of particle contamination in the chamber is materialdeposited at the edge or on the backside of the substrate that flakesoff or peels off during a subsequent process. Substrate edges aretypically beveled, making deposition difficult to control over thesesurfaces. Thus, deposition at substrate edges is typically nonuniformand, where metal is deposited, tends to adhere differently to adielectric than to silicon. If a wafer's dielectric layer does notextend to the bevel, metal may be deposited on a silicon bevel andeventually chip or flake, generating unwanted particles in the chamber.Additionally, chemical mechanical polishing is often used to smooth thesurface of a substrate coated with tungsten or other metals. The act ofpolishing may cause any deposits on the edge and backside surfaces toflake and generate unwanted particles.

A number of approaches have been employed to control the deposition onthe edge of the substrate during processing. One approach employs ashadow ring which essentially masks a portion of the perimeter of thesubstrate from the process gasses. One disadvantage with the shadow ringapproach is that, by masking a portion of the substrate's perimeter, theshadow ring reduces the overall useful surface area of the substrate.This problem is made worse if the shadow ring is not accurately alignedwith the substrate, and alignment can be difficult to achieve.

Another approach employs a purge ring near the edge of the substrate fordelivering a purge gas along the substrate's edge to prevent edgedeposition. The purge gas limits or prevents the deposition gas fromreaching the substrate and thus limits or prevents deposition on thewafer's beveled edge. A third approach uses a shutter ring and a purgering in combination to form a purge gas chamber having a purge gas inletand outlet adjacent the substrate's edge so as to guide the purge gasacross the wafer's edge.

A wafer typically sits inside (radially) the purge ring, with a gaptherebetween. Conventionally, purge rings are made of aluminum and arewelded to the substrate support in an effort to prevent the ring fromdeforming during processing. However, during the thermal cycling whichoccurs within a CVD processing chamber, the aluminum rings nonethelessdeform, losing the integrity of their shape and therefore compromisetheir ability to keep particles from depositing on the substrate's edge.This can change the size of the gap, leading to non-uniformity ofdeposition across the wafer's edge. As the aluminum rings expand andcontract, material thereon can flake, and create particles which cancontaminate the wafer.

Further, in order for the rings to work effectively for shadowing and/orfor purging, they must be frequently cleaned to remove depositionmaterial which can alter the gap or flake off and contaminate the wafer.Such cleaning increases chamber downtime, reduces throughput and resultsin higher operating costs.

Accordingly a need exists for an improved susceptor which can reliablyprevent edge deposition, and which can be easily cleaned.

SUMMARY OF THE INVENTION

In one aspect, the present invention overcomes the problems of the priorart by providing a substrate support having a removable edge ring, whichmay be made of a material having a lower coefficient of thermalexpansion (CTE) than that of the substrate support. The edge ring may bea shadow ring, a purge ring, or function as both edge ring and shadowring. The edge ring and the substrate support are configured for pin andslot coupling. In one aspect, either the edge ring or the substratesupport includes a plurality of pins, and the other of the edge ring orthe substrate support includes a plurality of alignment slots in whichthe pins may be inserted. Each of the slots is at least as wide as acorresponding one of the plurality of pins and extends in the radialdirection to a length, which is sufficient to compensate for thedifference in thermal expansion between the substrate support and theedge ring.

In another aspect, the invention provides a removable first edge ringpositioned above the substrate support and configured for pin and slotcoupling with a second edge ring attached to the substrate support.Preferably, either the first edge ring or the second edge ring includesa plurality of pins, and the other of the first edge ring or second edgering includes one or more alignment recesses and one or more alignmentslots. The pins are inserted into the alignment recesses and alignmentslots to couple the two edge rings in alignment. Each of the alignmentrecesses and alignment slots are at least as wide as the correspondingone of the plurality of pins, and each of the alignment slots extends inthe radial direction to a length that is sufficient to compensate forthe difference in thermal expansion between the first edge ring and thesecond edge ring.

Other objects, features and advantages of the present invention willbecome more fully apparent from the following detailed description ofthe preferred embodiments, the appended claims and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a susceptor of the invention;

FIG. 2 is a side view, in pertinent part, of a susceptor of theinvention;

FIG. 3 is a side view, in pertinent part, of a susceptor of theinvention;

FIG. 4 is a side view in pertinent part of a susceptor of the invention;

FIGS. 5A and 5B are side views in pertinent part of a susceptor of theinvention;

FIG. 6 is a side view in pertinent part of a susceptor of the invention;

FIG. 7 is a side view of a chamber showing a susceptor of the inventionin a non-processing position.

FIG. 8 is a top view of a purge ring of the invention.

FIG. 9 is a top view of a shadow ring supported on a chamber body ringof the invention;

FIG. 10 is a side view of a chamber showing a susceptor of the inventionin a processing position; and

FIG. 11 is a side view of a chamber showing a susceptor of theinvention.

DETAILED DESCRIPTION THE PREFERRED EMBODIMENT

FIG. 1 is an exploded perspective view of a susceptor 11 a. Thesusceptor 11 a comprises a substrate support 13, adapted for pin andslot coupling with an edge ring, such as purge ring 15. Specifically,the substrate support 13 comprises three pins 19 a-c which extendupwardly from the top surface of substrate support 13. The bottomsurface of the purge ring 15 comprises three alignment slots 17 a-cpositioned to interface with the three pins 19 a-c. The substratesupport 13 comprises a central wafer supporting surface 13 a, and thethree pins 19 a-c are disposed substantially equally spaced around thesubstrate supporting surface 13 a. Each of the slots 17 a-c is at leastas wide as the corresponding pin 19 a-c, and extends radially outwardfrom the center of the substrate supporting surface 13 a, in thedirection in which the substrate support 13 expands and contracts duringthermal cycling.

The substrate support 13 is preferably made of a metal such as aluminum,as is conventional. The purge ring 15 is generally made of a materialhaving a lower coefficient of thermal expansion (CTE) than the CTE ofthe substrate support 13 material. Preferably the purge ring 15 is madeof a ceramic material. The slots 17 a-c extend a length which issufficient to compensate for the difference in thermal expansion betweenthe substrate support 13 and the purge ring 15, over the range ofprocess temperatures to which the susceptor 11 a is exposed. Thisdifference in thermal expansion may be due to the different CTE of thepurge ring 15 material and the substrate support 13 material. Preferablyeach pin 19 a-c is surrounded by a pad 21 made of a thermally insulatingmaterial, so as to achieve thermal insulation between the substratesupport 13 and the purge ring 15, as further described below withreference to FIG. 2. The pads 21 are preferably made of a highlypolished ceramic and therefore allow the purge ring 15 to slide easilytherealong while minimizing particle generation. The purge ring 15 mayfurther include a plurality of wafer guide pins 23 to facilitateaccurate wafer placement, as is disclosed in U.S. patent applicationSer. No. 09/103,462 filed Jun. 24, 1998 (incorporated herein in itsentirety).

FIG. 2 is a side view, in pertinent part, of a susceptor 11 a, having awafer W positioned thereon. As shown in FIG. 2 the substrate support 13,the purge ring 15 and the slots 17 a-c are configured such that with useof the pad 21, no direct contact exists between the substrate support 13and the purge ring 15. By thermally insulating the purge ring 15 fromthe metal substrate support 13, the purge ring 15 experiences lessthermal stress then would otherwise result if the purge ring 15 were todirectly contact the typically higher temperature substrate support 13.Also as shown in FIG. 2, the slot 17 a has a depth greater than thelength of the pin 19 a to reduce thermal conduction from the substratesupport 13 to the purge ring 15, via the pin 19 a.

The slots 17 a-c extend radially outward relative to the center of thesubstrate support 13 and preferably are each just slightly wider thanthe respective pin 19 a-c. This prevents the purge ring 15 movementlaterally relative to the substrate support occuring as a result ofthermal cycling induced expansion and contraction from being more thanthe maximum distance allowing clearance between the slot 17 a and thepin 19 a pair. The pins 19 a-c also restrict rotational movement of thepurge ring 15 relative to the substrate support 13, thereby providingrotational alignment.

The substrate support 13 comprises a purge gas delivery channel 25 and adiffuser ring 13 b which couples purge gas from the purge gas deliverychannel 25 through a purge gas distribution channel 27 defined by aninner edge of the diffuser ring 13 b and an outer edge of the substratesupport 13, and then through a plurality of small orifices O formed inthe diffuser ring 13 b to a lower edge of the purge ring 15.

In operation the wafer W is positioned on the wafer supporting surface13 a such that the edge of the wafer W is positioned adjacent the outletof the purge slot 29. In this manner as purge gas flows upwardly throughthe purge slot 29 along the edge of the wafer W, deposition on thewafer's edge is prevented. During a deposition process, the susceptor 11a is typically heated to a temperature in the range of 350° to 475° C.,typically by a heating coil embedded in or contacted with the undersideof, the susceptor 11 a. However, for chamber maintenance or cleaning,the susceptor 11 a is typically allowed to cool back to ambienttemperatures.

This temperature change causes thermal expansion and contraction of thechamber elements, including the substrate support 13 and the purge ring15. Despite thermal cycling which occurs during CVD processing, and theresulting expansion and contraction of the substrate support 13 and thediffuser ring 13 b, thermally induced stresses are not imposed upon thepurge ring 15, as it (and the pins 19 a-c supporting it) can moveradially as the temperature changes, due to the pin 19 a-c and slot 17a-c coupling. Any thermally induced expansion of the gap between thepurge ring 15 and the wafer W is insignificant. Accordingly edgedeposition is more uniformly and reliably prevented. Moreover, the purgering 15 may be easily lifted off the pins 19 a-c for routine cleaning orreplacement. Accordingly downtime is minimized.

FIG. 3 is a side view, in pertinent part, of a susceptor 11 b. Theinventive susceptor 11 b of FIG. 3 is similar to the susceptor 11 a ofFIG. 2, except the substrate support 13 of FIG. 3 does not comprise thediffuser ring 13 b. Instead, the purge gas delivery channel 25 deliverspurge gas to a purge gas distribution channel 27 which is defined by aninner edge of the purge ring 15 and an outer edge of the substratesupport 13, as is the more narrowly defined purge gas slot 29. Theembodiment of FIG. 3 requires fewer parts, and replaces the orifices O(of FIG. 1) with a restrictor gap R. The restrictor gap R is formed by ahorizontal notch in the substrate support 13 and a correspondinghorizontal protrusion in the purge ring 15. The size of the restrictorgap R is determined by the respective vertical dimensions of thesubstrate support 13 and the purge ring 15 to the horizontal notch orprotrusion, and by the thickness of the pad 21. The embodiment of FIG. 3reduces clogging because the restrictor gap R which expands radiallyaround the substrate support 13 in a continuum is less likely to clogthan are the plurality of orifices. By reducing the number of parts, theFIG. 3 embodiment also reduces the probability of differential expansiontherebetween and the resultant particle generation. Note that, like theFIG. 1 and 2 embodiment, the purge ring 15 rests on the insulator pads21 and is aligned by the pins 19.

FIG. 4 is a side view, in pertinent part, of a susceptor 11 c. As shownin FIG. 4, the purge ring 15 of the inventive susceptor 11 c has aplurality of pins 19 (only one shown) which extend downward from thebottom surface of the purge ring 15. The pins 19 are pressed into thepurge ring 15 and the pads 21 are secured to the pins 19 in the samemanner, or maybe integral to the pins 19. In operation, each pin 19 isinserted within a corresponding slot 17 located on the substrate support13. In this example the slots 17 are formed in the diffuser ring portion13 b of the substrate support 13. Thus, FIG. 4 shows that the positionsof the pins 19 and the slots 17 may be switched, and still achieve theadvantages of pin and slot coupling.

FIGS. 5A and 5B are side views, in pertinent part, of a susceptor 11 d.The inner edge 15 a of the purge ring 15 of FIGS. 5A and 5B isconfigured such that the inner edge 15 a overhangs the edge of the waferW. Thus, the inner edge 15 a of the purge ring 15 functions as both apurge ring and a shadow ring overhanging or shadowing the wafer's edge.The pin and slot coupling of FIGS. 5A and 5B allows the substratesupport 13 to expand and contract without effecting the shape orposition of the inner edge 15 a of the purge ring 15, as described abovewith reference to FIGS. 2 and 3, and is referred to in this applicationas self-aligning and non contact. FIG. 5A shows the purge ring 15 andthe inner edge 15 a of the purge ring 15 in a process position, and FIG.5B shows the purge ring 15 and the inner edge 15 a of the purge ring 15in a wafer W transfer position. Because purge ring 15 overlaps thewafer's edge, the purge ring is conventionally supported in a wafer Wtransfer position above the substrate support 13 (e.g., by a hanger orlip which protrudes form the chamber wall) while a wafer W is placed onor extracted from the substrate support 13. After a wafer W is placed onthe substrate 13, the substrate support 13 elevates and engages thebottom of the purge ring 15, transferring the purge ring 15 from the lipto the substrate support 13 as further described below.

Conventional substrate supports 13, whether to be used with a purge ring15 and/or shadow ring 4, are initially lowered to a wafer W transferposition. A wafer handler then carries a wafer W into position above thesubstrate support 13 and the lift pins (not shown) lift the wafer W offthe wafer handler. Thereafter, the wafer handler retracts, and thesubstrate support 13 is further elevated to engage the shadow ring 4.

FIG. 6 is a side view in pertinent part of a susceptor 11 e. Theinventive susceptor 11 e is configured to facilitate access to the purgegas distribution channel 25 for cleaning. Specifically, the surface ofthe substrate support 13 in which the pin 19 (or in an alternativeembodiment, the slot 17) is located, is below the outlet of the purgegas distribution channel 25. Thus, when the purge ring 15 and/or shadowring 4 is removed from the substrate support 13, the gas distributionchannel's outlet is exposed. To further facilitate cleaning, the purgegas distribution channel 25 may be angled upwardly (preferably between0° and 30°), as shown in FIG. 6.

FIG. 7 is a side view of a chamber showing a susceptor 11 f of theinvention in a lowered non-processing position. The susceptor 11 fcomprises a removable first edge ring, such as a shadow ring 4,supported by a chamber body ring 200 disposed on the internal surface102 of the processing chamber body 100 above the substrate support 13and a second ring, such as a purge ring 15, disposed on the substratesupport 13. The purge ring 15 may be attached to the substrate support13 as described above relating to FIGS. 1-6. The substrate support maybe made of various materials, such as aluminum and ceramic, and mayinclude a heating element, such as a resistive heating coil. The shadowring 4 comprises a plurality of tapered or frustoconically shaped pins19 (two shown), equally spaced around the perimeter of the shadow ring 4and extending downwardly therefrom. The purge ring 15 includes at leastone tapered or frustoconically shaped alignment recess 5 and at leastone tapered or frustoconically shaped alignment slot 6 formed therein.Although the invention is shown and described with a shadow ring havingpins thereon and a purge ring having recess/slot thereon, it isunderstood that invention contemplates embodiments wherein the pin andrecess/slot coupling may be disposed on either the shadow ring or thepurge ring. The invention also contemplates embodiments wherein eitherthe pins or the recesses/slots include tapered surfaces.

The pins 19 are positioned to interface with the alignment recess 5 andthe alignment slot 6. The alignment recess 5 and the alignment slot 6are at least as wide as a corresponding one of the plurality of pins 19.In one aspect, the width is defined as the dimension perpendicular tothe radial direction, relative to the center of the purge ring 15.Referring to FIG. 8, which is a top view of a purge ring 15 of theinvention showing the alignment recess 5 and the alignment slot 6, line800 represents the radial direction relative to the center of the purgering 15, and line 802 represents the direction perpendicular to theradial direction relative to the center of the purge ring 15. The widthof the alignment slot 6, being the dimension perpendicular to the radialdirection relative to the center of the purge ring 15, is shown bysegment 804. The radial dimension of the alignment slot 6 is shown bysegment 806. The alignment slot 6 extends in a radial direction,relative to the center of the purge ring 15, a length that is sufficientto compensate for any difference in thermal expansion between the purgering 15 and the shadow ring 4. The radial dimension (i.e., length) ofthe alignment slot 6 is up to about sixty mils greater, preferably up toabout forty mils greater, than the radial dimension of the correspondingpin 19. The width of the alignment recess 5 and alignment slot 6 isbetween about three mils and about ten mils wider, preferably betweenabout three mils and about eight mils wider, than the width of thecorresponding pin 19. The coupling of the pins 19 with the alignmentrecess 5 and the alignment slot 6 restricts movement of the shadow ring4 caused by thermal cycling induced expansion and contraction or othercauses to less than the length of the alignment slot 6. The pins 19 alsorestrict rotational movement of the shadow ring 4 relative to the purgering 15, thereby providing rotational alignment.

The pins 19 as shown in FIG. 7 preferably have a frustoconical shape,tapering from a base portion to a top portion. The alignment recess 5and the alignment slot 6 have matching tapering sidewalls forming awider opening portion and a narrower bottom portion for receiving thetapered pins 19. This configuration allows for and corrects grossmisalignment between the two rings because the narrower tip portion ofthe pins 19 can be inserted into the wider opening portion of the recess5 and slot 6 with a greater margin of misalignment. Thus, withfrustoconically shaped or tapered pins 19 instead of non-tapering (i.e.,cylindrical) pins, recess 5, and slot 6, misalignment of the shadow ring4 with the purge ring 15, due to thermal expansion or other causes canbe corrected when the pins 19 are inserted into the recess 5 and slot 6when the rings come together. As the pins 19 are inserted into therecess 5 and slot 6, misalignment between the shadow ring and the purgering is corrected as the surface of the pin 19 slides along the surfacedefined by the recess 5 or slot 6. The two rings are aligned as the pins19 are fully inserted into the recess 5 and slot 6.

The pin 19 and recess 5/slot 6 coupling allows the shadow ring 4 to movewith respect to the purge ring 15 due to different thermal expansionsbetween the two rings without imposing stresses on either ring thatcould cause ring deformation, flaking or breakage of any of thecomponents. The shadow ring 4 remains in pivotal alignment to the purgering 15 at the location of the pin 19 and recess 5 coupling, while thepin 19 and slot 6 coupling allows the shadow ring to move slightly(i.e., restricted by the length of the slot 6) relative to each otherdue to different thermal expansions between the two rings. The inventionprovides consistent alignment of the shadow ring 4 with the purge ring15 and the substrate. Moreover, the shadow ring 4 may be easily removedfor cleaning or replacement. Down time is thereby minimized.

FIG. 9 is a top view of a shadow ring 4 supported on a chamber body ring200. A chamber body ring 200 is secured to the internal surface 102 ofthe chamber body 100. The chamber body ring 200 includes a plurality ofrecesses 202 formed in the upper portion of the internal surface 220 ofthe chamber body ring 200. The shadow ring 4 includes a plurality ofprojections 10 configured to rest on the surface of the chamber bodyring 200 defined by the recesses 202. Preferably, four projections 10are spaced equally along the perimeter of the shadow ring 4. When notcoupled to the purge ring 15, the shadow ring 4 may be supported by thechamber body ring 200 via the projections 10 resting on the surface ofthe recesses 202. The recesses 202 are sized to allow for thermalexpansion of the shadow ring 4, and yet keep the shadow ring 4sufficiently aligned with the purge ring 15 so that the pins 19 staywithin the capture range of the recess 5 and slot 6. The sidewallsurfaces of the recess 202 may also be tapered to urge a shadow ring 4into the desired aligned position on the chamber body ring 200.

FIG. 10 is a side view of a chamber showing a susceptor 11 f in aprocessing position. As shown, the purge ring 15 attached to thesubstrate support 13 contacts and lifts the shadow ring 4. The pins 19of the shadow ring 4 are inserted into the recess 5 and slot 6 of thepurge ring 15. The shadow ring 4 is thereby lifted off the chamber bodyring 200, so that the projections 10 of the shadow ring 4 are lifted offthe internal surface 220 of the chamber body ring 200 defined by therecesses 202. In this configuration, the shadow ring 4 is positionedabout 3 to 5 millimeters above a wafer W and overhangs a portion of theperimeter, or edge, of the wafer W, preventing deposition thereon duringCVD processing.

In operation, the substrate support 13 is initially lowered to a wafertransfer position, as shown in FIG. 7. A wafer handler comprising arobot blade then carries a wafer into position above the substratesupport 13. Lift pins (not shown) lift the wafer W off the robot blade,and the robot blade retracts. The substrate support 13 is elevated toposition the substrate thereon, and then the substrate support 13further elevates so that the purge ring 15 attached thereto lifts theshadow ring 4 off the chamber body ring 200, as shown in FIG. 10. As thepurge ring 15 engages the shadow ring 4, the pins 19 are inserted intothe alignment recess 5 and alignment slot 6. The tapered surfaces of thepins 19 slides along the tapered surfaces of the alignment recess 5 andalignment slot 6, urging the shadow ring 4 into desired alignment withthe purge ring 15.

FIG. 11 is a side view of a chamber showing a susceptor 11 g in anon-processing configuration. In this aspect of the invention, thesubstrate support 13 includes a ceramic susceptor and a ceramic purgering 15 disposed thereon. The purge ring 15 and the shadow ring 4include the pin and slot/recess coupling of the invention as describedabove.

As is apparent from the above description, a chamber such as the chamberdescribed in commonly assigned U.S. patent application Ser. No.09/103,462, filed Jun. 24, 1998 (incorporated in its entirety), whenemploying the inventive susceptor of FIGS. 1 through 5, providessuperior edge deposition prevention and increased throughput as comparedto conventional deposition chambers (CVD, PVD, etc.).

The foregoing description discloses only the preferred embodiments ofthe invention, modifications of the above disclosed apparatus and methodwhich fall within the scope of the invention will be readily apparent tothose of ordinary skill in the art. For instance, the inventivesusceptor comprises pin and slot coupling between any type of edge ring(purge ring and/or shadow ring), whether the pins are located on thesubstrate support or the ring. Although each of the figures shows theuse of thermally insulating pads these pads are optional. Further, itwill be understood that a heating element may be included in thesusceptor, as is conventionally known. Also as conventionally known,each of the purge gas delivery channels 25 of the various embodiments ofthe invention preferably open into a purge gas distribution channel 27which also extends somewhat below the opening of the purge gas deliverychannel 25 (as shown in each of the figures), so as to create a bufferchannel which ensures more even distribution of the purge gas to thepurge slots 29.

The terms pin and slot are to be broadly interpreted to include shapesother than straight pins and slots 6 (e.g., rectangular keys, etc.).Further, purge ring or purge ring/shadow ring can be advantageouslyremovably coupled to a substrate support, by mechanisms other than pinand slot coupling. Any removably coupled purge ring will benefit fromthe exposed outlet of the purge gas delivery channel and the upwardlyangled purge gas delivery channel. Similarly a susceptor whether or nothaving a removably coupled purge ring, can benefit from the definitionof a purge gas distribution channel having a restrictor gap between thesubstrate support and the purge ring. Thus, these aspects of theinvention should not be respectively limited to pin and slot coupling orto removably coupled purge rings.

While the present invention has been disclosed in connection with thepreferred embodiments thereof, it should be understood that otherembodiments may fall within the spirit and scope of the invention, asdefined by the following claims.

What is claimed is:
 1. An apparatus for processing substrates,comprising: a chamber; a substrate support disposed in the chamber; afirst edge ring disposed on the substrate support, wherein the firstedge ring comprises one or more tapered recesses and one or more slots;and a second edge ring having two or more matching tapered pins disposedthereon for mating engagement with the recesses and slots of the firstedge ring.
 2. The apparatus of claim 1, further comprising: a chamberbody ring disposed on an interior surface of the chamber, the chamberbody ring having one or more recesses for supporting engagement with thesecond edge ring.
 3. The apparatus of claim 2 wherein the first edgering comprises a urge ring.
 4. The apparatus of claim 2 wherein thesecond edge ring comprises a shadow ring.
 5. The apparatus of claim 2wherein the first edge ring includes one tapered recess and onediametrically positioned tapered slot, and wherein the second edge ringincludes two tapered pins diametrically positioned for mating engagementwith the recess and the slot.
 6. The apparatus of claim 2 wherein thesubstrate support comprises a purge gas channel, and the first edge ringcomprises a purge ring.
 7. The apparatus of claim 2 wherein the one ormore recesses on the chamber body ring include tapered side surfaces. 8.The apparatus of claim 1, wherein the first edge ring is made of amaterial having a lower coefficient of thermal expansion (CTE) than thatof the substrate support.
 9. The apparatus of claim 1, wherein the oneor more slots of the first edge ring extend in a radial direction,relative to the center of the first edge ring, to a length that issufficient to compensate for any difference in thermal expansion betweenthe first edge ring and the second edge ring.
 10. The apparatus of claim1, wherein the radial dimension of the one or more slots of the firstedge ring is up to about 60 mils greater than the radial dimension ofthe one or more matching tapered pins of the second edge ring.
 11. Theapparatus of claim 1, wherein the width of the one or more taperedrecesses and one or more slots of the first edge ring is between about 3mils and about 10 mils wider than the width of the one or more matchingtapered pins of the second edge ring.
 12. The apparatus of claim 1,wherein each of the one or more tapered pins of the second edge ring issurrounded by an insulating pad made of a thermally insulating material.13. The apparatus of claim 1, wherein the substrate support furthercomprises one or more matching tapered pins disposed thereon for matingengagement with the recesses and slots of the first edge ring.
 14. Theapparatus of claim 13, wherein each of the one or more tapered pins ofthe substrate support is surrounded by an insulating pad made of athermally insulating material.
 15. An apparatus comprising: a chamber; asubstrate support; a first edge ring disposed on the substrate support,comprising two or more tapered pins; a second edge ring, comprising oneor more tapered recesses and one or more slots, in mating engagementwith the two or more tapered pins of the first edge ring; and a chamberbody ring disposed on an interior surface of the chamber, wherein thechamber body ring comprises one or more recesses for supportingengagement with the second edge ring.
 16. The apparatus of claim 15,wherein the first edge ring is made of a material having a lowercoefficient of thermal expansion (CTE) than that of the substratesupport.
 17. The apparatus of claim 15, wherein the one or more slots ofthe second edge ring extend in a radial direction, relative to thecenter of the second edge ring, to a length that is sufficient tocompensate for any difference in thermal expansion between the firstedge ring and the second edge ring.
 18. The apparatus of claim 15,wherein the radial dimension of the one or more slots of the first edgering is up to about 60 mils greater than the radial dimension of the oneor more matching tapered pins of the second edge ring.
 19. The apparatusof claim 15, wherein the width of the one or more tapered recesses andone or more slots of the second edge ring is between about 3 mils andabout 10 mils wider than the width of the one or more matching taperedpins of the first edge ring.
 20. The apparatus of claim 15, wherein eachof the one or more tapered pins of the first edge ring is surrounded byan insulating pad made of a thermally insulating material.
 21. Theapparatus of claim 15, wherein each of the one or more tapered pins ofthe chamber body ring is surrounded by an insulating pad made of athermally insulating material.
 22. The apparatus of claim 15, whereinthe substrate support comprises a purge gas channel, and the first edgering comprises a purge ring.
 23. An apparatus for processing substrates,comprising: a chamber; a substrate support disposed at least partiallyin the chamber; a first edge ring disposed on the substrate support,comprising one or more tapered recesses and one or more slots; a secondedge ring disposed in mating engagement with the first edge ring,comprising two or more tapered pins; and a chamber body ring disposed onan interior surface of the chamber, wherein the chamber body ringcomprises one or more tapered recesses for supporting engagement withthe second edge ring.
 24. The apparatus of claim 23, wherein thesubstrate support comprises a purge gas channel, and the first edge ringcomprises a purge ring.
 25. An apparatus for processing substrates,comprising: a chamber; a substrate support, disposed at least partiallyin the chamber, comprising a purge gas channel; a purge ring, disposedon the substrate support, comprising one or more tapered recesses andone or more diametrically positioned slots; a shadow ring, comprisingtwo or more tapered pins diametrically positioned for mating engagementwith the recesses and slots of the purge ring; a chamber body ringdisposed on an interior surface of the chamber, wherein the chamber bodyring comprises one or more tapered recesses for supporting engagementwith the shadow ring.
 26. An apparatus for processing substrates,comprising: a chamber; a substrate support, disposed at least partiallyin the chamber, comprising a purge gas channel; a purge ring disposed onthe substrate support, comprising two or more tapered pins; a shadowring, comprising one or more tapered recesses and one or more slots,disposed in mating engagement with the two or more tapered pins of thepurge ring; and a chamber body ring disposed on an interior surface ofthe chamber, wherein the chamber body ring comprises one or more taperedrecesses for supporting engagement with the shadow ring.